package linkedlistskills;

public class solution21 {

    public class ListNode {
        int val;
        ListNode next;
        ListNode() {}
        ListNode(int val) { this.val = val; }
        ListNode(int val, ListNode next) { this.val = val; this.next = next; }
    }
    public ListNode mergeTwoLists(ListNode list1, ListNode list2) {
        /*先设置一个虚拟头指针*/
        ListNode dummy = new ListNode(-1);
        ListNode p = dummy;

        ListNode p1 = list1;
        ListNode p2 = list2;

        while(p1!=null && p2!=null){
            if (p1.val>p2.val){
                p.next = p2;
                p2 = p2.next;
            }else {
                p.next = p1;
                p1=p1.next;
            }
            p=p.next;
        }

        if (p1==null){
            p.next = p2;
        }
        if (p2==null){
            p.next = p1;
        }

        return dummy.next;
    }
}
